1. The Field of the Invention
This invention relates to methods for repairing teeth, and more particularly to such methods of tooth repair as involve partial amputation of the coronal pulp so that the vitality of the remaining pulp is maintained and the repaired tooth can function as a healthy biological unit.
2. The Background Art
When traumatic injury or the advancement of a carious lesion through the enamel and dentin of a tooth exposes the pulpal tissue to infection, various endodontic procedures may be appropriate to repair and preserve the tooth involved. In one of these, the vital dental pulpotomy, an effort is made to preserve healthy pulpal tissue in the pulp canals in the roots of the tooth.
In fully developed adult secondary teeth, such procedures are only occasionally undertaken. Instead, pulpal tissue is completely removed from the crown and root canals of the tooth and replaced by various materials in order to establish a seal to the canal openings at the root ends.
Nevertheless, many circumstances demand that all possible efforts be exercised in order to repair such teeth in a manner which retains at least a minimal amount of vitality therein. Typically, this will mean retaining the portion of the pulpal tissue in the pulp canals and replacing only the balance of that tissue with a suitable filling.
In the practice of dentistry for children, the conservation of the vitality and health of at least a portion of the dental pulp is a most important preventative health practice. No space-maintaining appliance can equal the natural primary tooth of the child during the development years. Neither can the psychological value of the retention of natural teeth be over estimated in developing the commitment of a child to its own dental hygiene.
In addition, primary teeth exhibit special structural characteristics which may make the full removal of pulpal tissue difficult in endodontic procedures. The root canals in such teeth tend to have cross sections that are more flat and ribbon-like than in adult teeth. This is particularly true as a primary tooth matures.
Root resorption in primary teeth requires that, if the pulpal tissue in root canals is removed, the filling used to replace that tissue, at least in the area of the roots of the teeth, must be capable of resorption with the rest of the root. This may undesirably limit the types of filling materials to which a practitioner may resort during dental repair.
Other circumstances also call for retention of vital pulpal tissue in the root canals of an injured or carious tooth. In young immature permanent teeth, the apical foramen may not have completely closed, thereby complicating any endodontic procedure in which removal of vital pulpal tissue from that portion of the tooth must be effected. In addition, select specific circumstances may even call for the vital dental pulpotomy in developed permanent teeth.
A vital dental pulpotomy involves the amputation of the vital coronal pulp down to the orifices of the pulp canals. This is usually accomplished by accessing the roof of the pulp chamber and using an excavator to remove the portion of the dental pulp desired. Frequently, bleeding in this stage of the procedure can be substantial and difficult to curtail, as the presence of a beginning infection in the pulpal tissue will normally stimulate blood flow thereto.
It is this increase in blood flow and the concomitant swelling that are the source of the pain which alerts a patient to seek dental help. Nevertheless, hemorrhaging must be arrested before further steps of the procedure can be undertaken. This is usually accomplished using dry cotton pellets or cotton pellets moistened with a hemostatic composition. The pellets are placed in the bottom of the excavated coronal pulpal chamber against the exposed ends of the pulpal tissue in the root canals. Other chemicals, such as formacresol, may be used; however, they are all too frequently not adequate to produce prompt hemostasis.
Once bleeding has been brought under control, a suitable drug is applied to the exposed cut ends of the pulpal tissue in order to inhibit bacterial activity at that site and in order to create thereat barrier regions of fixed pulpal tissue between the vital pulpal tissue in the pulp canals and the excavated coronal pulpal chamber. The barrier regions serve as buffers between the living tissue remaining and the filling placed in the coronal pulpal chamber in restoring the original tooth profile.
Unfortunately, several problems are inherent in such pulpotomy procedures. First, applying the hemostatic agent to the exposed cut ends of the pulpal material in the root canals is not always effective in bringing hemorrhaging under control rapidly enough to permit the complete restoration of the tooth in a single session with the patient. When hemorrhaging cannot be rapidly controlled, a two-stage pulpotomy is required. Initially, cotton pellets are sealed over the pulp stumps with a temporary filling, and thereafter the patient is forced to return for completion of the treatment some days later.
To an extent, the problem already described above is an inherent result of the fact that two distinct compounds, a hemostatic agent and a tissue fixing agent, must be applied in sequence to the ends of the cut pulpal tissues. The second application cannot occur until the hemostatic agent has been effective.
More significantly, however, the major drawback in prior methods of performing vital dental pulpotomies has been the character of the tissue-fixing compound applied to the cut ends of the pulpal tissue after hemorrhaging has been brought under control. It is necessary to fix the pulpal tissue at those sites in order to form between the vital pulpal tissue in the pulp canals and the material used to fill the coronal pulpal cavity a barrier that is bacteria-free, biocompatible, and stable. Prior to the present invention, the drug of choice for this purpose since the turn of the century has been formocresol--a mixture of formaldehyde and cresol. Unfortunately, formocresol is a known toxic, mutagenic, and carcinogenic material.
When employed in pulpotomies, formacresol causes undesirable local effects, as well as potential damage to liver and kidney tissues, which are remote from the treatment site. Among the harmful local effects noted are irritation of the tissues immediate to the treated tooth, abnormal levels of enamel defects in replacement permanent teeth, and rotation and displacement of those replacement teeth as they develop.
The literature has repeatedly called for the reevaluation of the use of formocresol in non-life threatening situations, such as pulpotomies. Examples of such literature are:
1. Loos et al., "An Enzyme Histochemical Study of the Effect of Various Concentrations of Formocresol on Connective Tissues," 31 Oral Surgery 571-85 (Apr. 1971).
2. Messer et al., "Long Term Effects of Primary Molar Pulpotomies on Succedaneous Bicuspids," 59 Journal of Dental Research 116-23 (Feb. 1980).
3. Meyers et al., "Tissue Change Induced by the Absorption of Formocresol from Pulpotomy Sites in Dogs," 5 Pediatric Dentistry 6-8 (1983).
4. Meyers et al., "Distribution of .sup.14 C-Formaldehyde After Pulpotomy with Formocresol," 96 Journal of the American Dental Association 805-13 (May 1978).
5. Lewis et al., "Formaldehyde in Dentistry: A Review of Mutagenic and Carcinogenic Potential," 103 Journal of the American Dental Association 429-34 (Sept. 1981).
6. Pashley et al., "Systemic Distribution of .sup.14 C-Formaldehyde From Formocresol-Treated Pulpotomy Sites," 59 Journal of Dental Research 602-7 (Mar. 1980).
7. Pruhs et al., "Relationship Between Formocresol Pulpotomies on Primary Teeth and Enamel Defects on their Permanent Successors," 94 Journal of the American Dental Association 698-700 (Apr. 1977).
8. Sipes et al., "The Use of Formocresol in Dentistry: A Review of the Literature," 17 Quintessence International 415-17 (1986).
9. Straffon et al., "Effect of Varying Concentrations of Formocresol on RNA Synthesis of Connective Tissue in Sponge Implants," 29 Oral Surgery 915-25 (June 1970).
Cumulatively, these and other studies have suggested that a search be undertaken to replace or reduce the use of formocresol in dental pulpotomies. Prior to the method of the present invention, such a replacement had not been located.
Thus, in relation to the performance of vital dental pulpotomies, a need exists to be able to promptly arrest hemorrhaging from the exposed cut ends of the pulpal tissue in the pulp canals so as to permit the subsequent steps of the pulpotomy procedure to be undertaken without delay. In this regard, it would be advantageous to be able to arrest hemorrhaging in situ in the pulpal tissue, rather than by a superficial application of a hemostatic agent thereto. In addition, a need exists to locate a composition with which to fix the exposed cut ends of such pulpal tissue after hemorrhaging has been arrested without introducing into the body a substance, such as formocresol, which causes deleterious effects on replacement teeth and local as well as remote body tissue. Finally, it would be highly advantageous to locate composition which could double both as a hemostatic and a tissue fixing agent when performing vital pulpotomies.